Our general setting for the house prioritises energy use as follows :
Solar » Battery » Grid
This means we minimise our usage of the grid when possible.
Given the cheap rate period of energy usage through the night, we had manually set the inverter to charge the battery from the grid during the core hours 23:30 - 05:30. This effectively stops the battery from being used to power the house in that period and we have no solar in that period bar the peak summer months.
Apologies for the lack of updates on the projects for managing solar, but something happened in January that changed everything.
My original solar installer wrote to us suggesting a battery upgrade for the house. They provided a lot of data on what we had used and when since the installation. They had a payback that was at around three years. Since I’d done a lot of the maths the previous year, I pushed all the data into a spreadsheet and it became obvious that this was the way forward for us.
After thinking about how to use the solar power my home generates in the most efficient way I realised that this is a generic problem. Effectively we have three types of devices in play :
Generation Sources. eg. my solar panels, the house battery, the grid. Switchable Consuming Devices. eg. My car, a heat pump, the house battery. The load generated by these devices can be turned on/off. Background Load. The overall usage at the site.
After creating the monitoring system for our solar installation earlier in the year I began to notice a few things about how it performed.
The solar output of the system is 9.6kWh and our house battery is around 10kWh. The battery system has a maximum charge rate that the panels often exceed. Whilst we get credit for energy exported back to the grid, the payment credit per kWh exported is approximately 8x less than the charge for 1kWh imported.
Now that we can pull the data from the local solar inverters, we need somewhere to store it. The excellent solismon3 discussed in the last post presents a simple page that Prometheus can consume to store the historic data.
The reporting partner to Prometheus is Grafana. This allows the creation of graphs/basic reporting of the data like this :
To bundle everything together I created two solismon3 docker images with the configuration for each inverter added.
As per the previous posts on this solar project, I had managed to identify that It was possible to talk to the data loggers connected to my inverters from my local network. Reading up further on this I found that loggers use a proprietary protocol (Solarman v5 protocol). Several fantastic folks have done the leg work on and built libraries that use Modbus type calls to pull the data.
The project that I had the best initial experience with was solismon3.
The data loggers that I discovered at the end of my installation have been connected to my home wifi by the installer. The default behaviour is that they probe the two inverters and send a burst of data to a cloud service every 5 minutes or so.
The loggers also have a local web interface that provides a way of controlling the device along with some basic data. The default username/password for these devices is admin/admin.
Last weekend we had 26 solar panels, some battery storage and a couple of inverters installed at the new house. All was installed fine and seems to be working OK so far. We went through a local county-based scheme with Solar Together. They awarded the Suffolk scheme to Greenscape Energy and turned around the install really quickly.
The installer walked me through the online app that monitors generation, consumption, storage and returned it to the grid.
